1. Technical Field of the Invention
The present invention relates to a wavelength converting device of a Quasi-Phase-Matched (QPM) Secondary-Harmonic-Generation system.
2. Related Art
Non-linear optical crystals, such as a lithium niobate single crystal and a lithium tantalate single crystal, have a high secondary non-linear optical constant. A periodic polarization inversion configuration can be formed in the crystal to produce a Quasi-Phase-Matched (QPM) Secondary-Harmonic-Generation (SHG) device. Further, an optical waveguide may be formed in the periodic polarization inversion configuration to produce a high efficient SHG device, leading to a wide variety of applications in optical communication, medical, photochemical and various optical measurement fields.
According to a harmonic wave oscillating device described in WO 2006/41172 A1, a thin plate of a ferroelectric single crystal is adhered onto a supporting body, and an upper side substrate is adhered thereon through a buffer layer and adhesive layer. A channel optical waveguide is formed in the thin plate. A periodic domain inversion structure is formed in the optical waveguide to convert the wavelength of a fundamental wave incident into the optical waveguide to oscillate a harmonic wave therefrom.
Further, Japanese patent publication No. 2004-254114A describes the technique of applying oxygen-deficient lithium niobate single crystal to lower its volume resistivity.
Japanese patent publication No. 2005-314137A describes applying Fe-doped lithium niobate to lower the volume resistivity.